Turbulators for the fire tubes in furnaces are well-known, some of which are shown in the following U.S. Pat. Nos.: 4,044,796 Smick, 2,640,194 Hytte, 2,660,198 Morrow, 3,185,143 Wilson, 2,591,398 Brock, 2,677,394 Brinen et al, 2,688,986 O'Brien.
All of these turbulators have as their purpose to break up laminar flow of gases through the fire tubes so as to improve heat transfer through the walls of the tube to the exterior body of water. In general, these turbulators comprise strips of metal bent into zig-zag form so that when the strip is inserted into a tube, gas passing therethrough will be variously deflected in an attempt to break up laminar flow.
What has not been realized previously is that when inserting the tubes, or later removing them for cleaning purposes, edges on the strips scratch the interior walls of the tubes, setting up areas or zones where corrosion by electrolysis and otherwise can more readily take place than otherwise would be the case. This shortens the life of the tubes. In fact, certain users have refrained from using turbulators because the advantages obtained by greater heat transfer is offset by the shorter life of the tubes.